Control system



Nov. 11, 1 B. WOODWARD CONTROL SYSTEM Fild Aug.

wzilll Inventor: Bernard Woodward, b if amy w y His Attorney.

Patented Nov. 11, 1941 CONTROL Bernard Woodward, Erie, Pa., assignor to General Electric Company, a. corporation of New York Application August 27, 1940, Serial No. 354,402

Claims.

My invention relates to control systems for multiple motor electric traction vehicles, and has for its object the provision of a new and improved power circuit arrangement for the traction motors of vehicles of this type.

It is a further object of my invention to provide an improved switching arrangement designed to prevent the generation of undesirable dynamic braking current.

It is well known to provide electrically driven vehicles with parallel connected motors or with a plurality of series connected groups of motors connected in parallel. Heretofore, it has been the practice to connect such traction motors to a source of supply in such a manner that when disconnected from the source the motors remained connected to each other in a loop circuit. As a, result of this arrangement undesirable dynamic braking currents are frequently generated, and such currents interfere with the operation of the vehicle and may have a deleterious effect upon the windings and commutators of the traction motors and their torque transmitting members.

The manner in which my invention avoids the above shortcomings of prior arrangements will be more clearly understood from a consideration of the following description taken in conjunction with the accompanying drawing, in which the single figure is a diagrammatic representation of an electric vehicle control system embodying my invention.

Referring now to the drawing, I have shown two motors l0 and II connected in parallel between a source of supply l2 and a ground connection l3. Associated with the motor I0 I have shown a, plurality of starting resistors l4, l5, and I6 adapted to be connected in various circuit relationships with the motor It, as will be further described hereinafter. The motor I I likewise has associated therewith a plurality of similar motor starting resistors l1, l8 and IS. A series field winding is arranged to be connected for operation of the motor [0 in either direction, while a series field winding 2| may be The cam switch 3| is connected to SYSTEIVI short circuit the starting resistors l4 and I5 through the wires 46 and 41. The cam switch 32 is connected to short circuit the starting resistors l5 and I6 through the wires and 48. The switches 33, 34 and 35 are similarly connected to the starting resistors IT, IS and I9 through the wires 49, 50, 5| and 52. The series field winding 20 is provided with two terminals and 56. The terminal 55 may be connected to one terminal of the motor In through the cam switch 21 and the wires 51 and 58, while it may be connected to ground through the cam switch 28 and the wires 51 and 59. The terminal 56 of the field winding 20 may be connected to one terminal of the motor [0 through the cam switch 26 and the wires 60 and 58, while it may be connected to ground through the cam switch 29 and the wires 60 and 59. The cam switches 26, 21, 28, and 29 therefore constitute a reversing controller for the series field winding 20 associated with the motor In. Through a group of similar connections the cam switches 36, 31, 38 and 39 constitute a reversing controller for the series field winding 2| associated with the motor II.

The traction motors l0 and H are shown arranged for connection to the source of supply l2 through a trolley 62 and a double-pole line breaker 65. The motor In maybe connected to the trolley 62 through the contacts 66 of the breaker, while the motor ll may be connected to the trolley 62 through the contacts 61 of the breaker 65. The line breaker is provided with an operating coil 68 which may be energized from the trolley I2 through a manually operated control switch 69, the wire 12, the cam switch 4|, the wire 13, the contacts 14 of the relay H, the operating coil 68, the normally closed contacts 15 of an over-current relay 16, the wire 11 and the cam switch 40 to ground.

In operation it may be assumed that the controller 25 is in its off position and that the manually operated control switch 69 is closed. In this position of the controller 25 the cam switch 42 is closed to complete an energizing circuit for the operating coil 18 of the undervoltage relay H. The undervoltage relay H will therefore have picked up and completed a holding circuit for itself through its normally open contacts 10. If now the master controller 25 is moved from its oil position to either of its zero positions, no change occurs in the positions of the switches 40, 4| and 42, but the proper cam switches controlling the field windings 20 and 2| are connected for operation of the motors in the selected direction. Proceeding now to the ter controller the cam switches 3| 62 through only the resistance l9.

first operating position of the controller 25, it will be observed that no change occurs in the connections of the power circuits through the cam switches 26 to 39 inclusive, but that the cam switches 40 and 4| are closed while the cam switch 42 is opened. Through the cam switches 40 and 4| and a circuit previously traced energization is applied to the operating coil 68 of the line breaker 65. The line breaker 65 therefore picks up simultaneously to connect the motors I and II in parallel to the trolley 62 through the contacts 66 and 61 respectively of the breaker 65 and to complete a holding circuit for itself around the cam switch 40 through its normally open contact 19. As the controller is moved to its second operating position the cam switches 30 and 33 are closed to short circuit the resistances l4 and I1 respectively and the cam switch 40 is opened. In this second and all subsequent operating positions of controller the cam switch 4| remains closed and the switches 40 and 42 remain open. As the accelerating cycle proceeds to the third operating position of the masand 34 are closed and the cam switches and 33 remain closed. This results in connection of the motor l0 to the trolley 62through only the resistance 6 and the connection of the motor II to the trolley If now the master controller 25 is moved to its fourth operating position the cam switches 30 and 33 are first opened and then the cam switches 32 and are closed. The'cam switches 3| and 34 remain closed. This results in connecting the motor I0 to the trolley 62 through the resistors l4, l5 and I6 in parallel and connecting the motor H to the trolley 62 through the resistors l8 and IS in parallel. In the fifth operating position of the master controller the cam switches 30 to 35 inclusive are all closed to connect the motors l0 and directly to the trolley 62.

If at any time during the operation of the motors Ill and H the voltage of the source of supply should fall to an undesirably low value, the undervoltage relay 1| will disable the energizing circuit of the operating coil 68 at the contacts 14 of the relay 1|. If a condition of overloadshould arise, an overload trip coil 80 of the overload relay 16 will disable the energizing circuit of the operating coil 6|! at the contacts 15, of the relay 16. If for any other reason it is desired to disconnect the motors l0 and H from the trolley 62, the master controller 25 may be thrown to its 0 position to disable the energizing circuit of the operating coil 68 at the cam switch 4|, or the control switch 69 may be opened to disable the circuit of the coil 68 at'this point. Regardless of the manner in which the line breaker 65 is opened, the motors ID and II will be disconnected from the trolley 62 at the contacts.

66 and 61 respectively of the line breaker 65. Since the contacts 66 and 61 are connected together on the line side of these contacts, the motors l0 and II remain connected together only through their ground connection when the line breaker 65 is open. It will now be apparent that no undesirable circulating currents may be generated in the motors H) and H when the line breaker 65 is in its open position,

It will be understood, of course, by those skilled in the art that my invention is not limited to the use of only two motors l0 and II connected in parallel, but that it maybe applied equally well where series connected groups of any number of traction motors are connected in parallel.

It will likewise be understood that my invention is equally applicable to any desired number of parallel circuits containing any desired number of series connected groups of motors.

While I have shown one form of my invention by way of illustration, it will be well understood by those in the art that I do not wish to be limited thereto, since many modifications are possible, andI, therefore, intend by the appended claims to cover all such modifications as fall within the true spirit and scope of myinvention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a traction motor system for an electrically driven vehicle, a plurality of electric traction motors, electricalconnections for connecting a first terminal of each of said motors to the same side of an electric supply source, a plurality of line contactors for connecting respectively the other terminals of said motors to the other side of, the supply source whereby said motors are connected in parallel with each other to said supply source and each of said motors is connected in a closed loop circuit including another of said motors, mechanical means connecting said contactors together for simultaneous operation and electrically operated means for opening said contactors while the first terminals of said motors remain connected to said same side of said supply source thereby to disconnect the other terminals of said motors from the other side of said supply source and disconnect said terminals from each other to disable the loop circuit for each of said motors.

2. In a traction motor system for an electrically driven vehicle, a plurality of electric traction motors, manually operable means for simultaneously connecting a first terminal of each of 'said motors to the same side of an electric supply source, switching means comprising a plurality of operatively interdependent line contacts arranged respectively to connect the other terminals of said motors to the other side of said supply source whereby said motors are connected in parallel with each other to said supply source and simultaneouslyeach of said motors is connected in a closed loop circuit including another of said motors, and electrical means for operating said switching means to open said line contacts while the first terminals of said motors remain connected to said same side of said supply source thereby to disconnect the other terminals of said motors from the other side of said supply source and disconnect said other terminals from each other to disable the loop circuit for each of said motors, whereby whenever said motors are deenergized said loop circuit is disabled.

3. In a traction motor system for an electrically driven vehicle, a plurality of electric traction motors having series field windings, manually operable controller means arranged to connect said series field windings in circuit with their respective motors and simultaneously to connect a first terminal of each of said motors to the same side of an electric supply source, a single switching mechanism having a plurality of operatively interdependent contacts arranged respectively to connect the other terminals of said motors to the other side of said supply source whereby said motors are connected in parallel with each other to said source of supply and simultaneously each of said motors is connected in a closed loop circuit including another of said motors, electromagnetic operating means for said switching mechanism, and means associated with said controller for controlling said operating means, whereby when said interdependent contacts are opened while the first terminals of said motors remain connected to said same side of said supply source said motors are deenergized and disconnected from each other to disable the loop circuit for each of said motors.

4. In a control system for an electrically driven vehicle, a plurality of electric traction motors, a permanently grounded manually operable controller, contact means associated with said controller and arranged to connect a first terminal of each of said motors to ground through said controller, single switching means comprising a plurality of operatively interdependent contacts arranged respectively to connect the other terminal of each of said motors to one side of an electric supply source thereby to connect said motors in parallel with each other to said source of supply and simultaneously to connect each of said motors in a closed loop circuit including another of said motors, and second contact means associated with said controller and arranged to control said switching means, whereby when said interdependent contacts are opened while said first terminals of said motors remain connected to ground said motors are deenergized and disconnected from each other to disable the loop circuit for each of said motors.

5. In a control system for an electrically driven vehicle, a plurality of electric traction motors having series field windings, a permanently grounded manually operable controller having contacts for connecting said series field windings in circuit with their respective motors and simultaneously connecting a first terminal of each of said motors to ground, a single switching mechanism having a plurality of operatively interdependent contacts arranged respectively to connect the other terminal of each of said motors to an electric supply source and simultaneously to complete a loop circuit including said motors, and means for operating said switching mechanism to open said contacts while said first terminals of said motors remain connected to ground thereby to disconnect said other terminals of said motors from said source of electric supply and to disconnect said other terminals from each other to disable said loop circuit.

BERNARD WOODWARD. 

